1. Field of the Invention
The present invention relates to an improvement in a fluid transmission system with a lock-up clutch, comprising a plurality damper springs accommodated in an annular arrangement in an annular spring-accommodating groove defined in a clutch piston of the lock-up clutch, a plurality of first transmitting claws provided on the clutch piston and each inserted between adjacent damper springs, and a plurality of second transmitting claws provided on a turbine impeller and each inserted between the adjacent damper springs in an opposed relation to the first transmitting claws.
2. Description of the Related Art
Such a fluid transmission system with a lock-up clutch is already known, as disclosed, for example, in Japanese Patent Application Laid-open No. 2001-198691.
In the known fluid transmission system with the lock-up clutch, to provide the plurality of second transmitting claws on the turbine impeller, an annular member made of a steel plate and having the plurality of second transmitting claws integrally formed thereon is welded to the turbine impeller.
The annular member provided with the second transmitting claws is fabricated by pressing, but the fabrication has a poor yield, which is an obstacle to a reduction in cost. Moreover, the number of the second transmitting claws formed on the one annular member is selected depending on the specification of the fluid transmission system and hence, a plurality of types of annular members having different numbers of second transmitting claws in dependence to fluid transmission systems of different specifications must be prepared, and thus, it is further difficult to reduce the cost. In addition, the annular member is welded over its entire periphery of the turbine impeller. This is accompanied by a problem that the turbine impeller receives a large quantity of heat during welding of the annular member and hence, a thermal strain is liable to be produced in the turbine impeller.
Accordingly, it is an object of the present invention to provide a fluid transmission system with a lock-up clutch, wherein the second transmitting claws can be fabricated with a good yield and are applicable commonly to various fluid transmission systems of different specifications, leading to a remarkable reduction in cost, and during welding of the second transmitting claws to the turbine impeller, the quantity of heat applied to the turbine impeller can be minimized, whereby the thermal strain of the turbine impeller can be suppressed.
To achieve the above object, according to a first feature of the present invention, there is provided a fluid transmission system with a lock-up clutch, comprising a plurality damper springs accommodated in an annular arrangement in an annular spring-accommodating groove defined in a clutch piston of the lock-up clutch, a plurality of first transmitting claws provided on the clutch piston and each inserted between adjacent damper springs, and a plurality of second transmitting claws provided on a turbine impeller and each inserted between the adjacent damper springs in an opposed relation to the first transmitting claws, wherein the plurality of second transmitting claws are welded to the turbine impeller in a separated and independent manner.
With the first feature, the plurality of second transmitting claws are separated and independent from one another and hence, a large number of transmitting claws can be fabricated with a good yield. Moreover, the transmitting claws are applicable to any of various fluid transmission systems by setting the number of second transmitting claws used and a mounting pitch freely depending on the specification of the fluid transmission system, leading to a remarkable reduction in fabrication cost.
In addition, the plurality of second transmitting claws are welded in a dispersed manner to the turbine impeller and hence, the turbine impeller receives a smaller quantity of heat, and thus, the thermal strain of the turbine impeller can be minimized.
Further, the plurality of second transmitting claws welded to the turbine impeller are separated from one another with no member obstructing the flow of a working fluid being present between the second transmitting claws and hence, the flow of the working fluid to the lock-up clutch is smoothened, which can contribute to an enhancement in responsiveness of the lock-up clutch.
According to a second feature of the present invention, in addition to the first feature, each of the second transmitting claws is comprised of a claw piece inserted between the adjacent damper springs, and a mounting base integrally connected to a root of the claw piece and having a width in a direction of rotation of the turbine impeller which is set at a value larger than that of the claw piece, opposite side ends of the mounting base arranged in the direction of rotation of the turbine impeller being welded to the turbine impeller.
With the second feature, the support span of each of the second transmitting claws in the direction of rotation can be set at a large value and hence, the second transmitting claws can withstand the transmission of a large torque sufficiently.
According to a third feature of the present invention, in addition to the second feature, opposite ends of a weld zone bonding each of the side ends of the mounting base and the turbine impeller to each other are extended to points outside the side ends.
With the third feature, the mounting base of each second transmitting claw is bonded to the turbine impeller particularly at an intermediate portion of the weld zone, which is in a good welded state, and hence, the mounting base can be bonded firmly to the turbine impeller.
According to a fourth feature of the present invention, in addition to the first feature, each of the second transmitting claws is comprised of a claw piece inserted between the adjacent damper springs, and a mounting base integrally connected to a root of the claw piece and having a width in a direction of rotation of the turbine impeller which is set at a value larger than that of the claw piece, opposite side ends of the mounting base arranged in the direction of rotation of the turbine impeller and an inner end of the mounting base opposite from the claw piece being welded to the turbine impeller.
With the fourth feature, the support span of each of the second transmitting claws in the direction of rotation can be set at a large value and hence, the second transmitting claws can withstand the transmission of a large torque sufficiently. Moreover, since the three sides of the mounting base are welded to the turbine impeller, the welding strength of the mounting base can be increased sufficiently.
The fluid transmission system corresponds to a torque converter T in each of embodiments of the present invention, which will be described hereinafter.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.